This invention is directed to a high density electrical connector utilizing a flexible film having etched circuitry thereon for electrically interconnecting to conductive traces or pads on at lease a pair of planar electronic devices, such as arranged at right-angle, mother/daughter-board fashion or in stacking styles for parallel board connection.
The architecture of complex computers, business machines, communication systems has largely developed around the use of a backplane, or mother board, which interconnects multiple daughter boards or cards carrying functioning components designed to define a host of memory and logic functions and the necessary electrical components to effect a signal generation and transmission. Various circuit paths on backpanel and daughter card are interconnected, typically through connectors which engage such circuit paths mechanically with a normal force between contact surfaces sufficient to establish a stable, low-resistance electrical path. Increasing circuit complexity has led to an increase in contact density to a point where hundreds of circuit paths must be interconnected between a given daughter card and a backplane, there being numerous daughter cards associated with a given backplane. This, in turn, has created mechanical problems in that the cumulative normal forces required to effect such an interconnection sometimes exceed 50 or 80 lbs. per card, per side of the card, and all are on extremely close centers, frequently in multiple rows on a given side of a card to require extremely accurate dimensions of the boards, connectors, contacts and the like. A still further problem has to do with the surface finishes of the contacts of connectors which may be contaminated in inventory or in handling and cause a variability in resistance between paths which, in the presence of high speed signal pulses transmitted therethrough alter the resistance and impedance of the circuit paths to a detriment of circuit function.
U.S. Pat. No. 5,171,154 represents a major effort to achieve a high density interconnection with high speed signal capability. A commercial system is described in Product Information Bulletin 65188 under the heading, "AMP-ASC INTERCONNECTION SYSTEMS," copyright 1991 by AMP Incorporated. A right-angle, backplane described therein shows a plurality of aligned spring carrier segments, where an essentially continuous groove running along the face of such segments includes plural, parallel grooves each containing a single canted coil spring. Typically, the segments are stacked alongside one another over a structural core member. A small gap normally exits between adjacent segments whereby the contained coiled spring can be trapped affecting proper spring operation, and ultimately causing connector performance problems. To overcome such problems, a thin metallic shim is normally placed into each spring groove or channel to bridge the small gaps. Thereafter, the springs are placed on top of the shim, whereby the shim provides an even, uninterrupted floor for the spring.
By a unique construction, the present invention achieves the goals of high density, high speed signal capability and simplicity in operation. This will become apparent in the specification which follows, particularly when read in conjunction with the accompanying drawings.